Devices and methods for balancing a high-pressure spool of a gas turbine engine

ABSTRACT

Devices and methods useful for balancing high-pressure spools of gas turbine engines are disclosed. An exemplary device may comprise: an input shaft configured to be coupled to an output of an accessory gear box driven by a high-pressure spool of a gas turbine engine; a first trigger rotatably coupled to the input shaft at a first speed ratio; and a sensor configured to detect the trigger at each revolution of the trigger. The first speed ratio may permit a rotational speed of the first trigger to be substantially the same as a rotational speed of the high-pressure spool. Upon detection of the trigger, the sensor may generate one or more signals representative of each associated revolution of the high-pressure spool of the gas turbine engine.

TECHNICAL FIELD

The disclosure relates generally to balancing of rotors of gas turbineengines, and more particularly to balancing of high-pressure spools ofgas turbine engines.

BACKGROUND OF THE ART

When determining a balancing solution for a rotor, vibration magnitudeand phase data are typically required. In most two-spool gas turbineengines, the phase data of the high-pressure spool is not availableduring normal operation. Accordingly, the acquisition of vibration andphase data for the balancing of the high-pressure spool is typicallyconducted while the high-pressure spool is rotated at sub-idle speedsand also while the engine is partially disassembled in order to visuallyexpose a portion of the high-pressure spool during balancing. Since thedynamic characteristics of the high-pressure spool can be quitedifferent at normal operating speeds than they are at reduced, sub-idlespeeds, the balancing solution acquired under such reduced speedconditions may not necessarily be ideal for typical operating conditionsof such gas turbine engines.

Improvement is therefore desirable.

SUMMARY

The disclosure describes components, devices and methods useful forbalancing of high-pressure spools of gas turbine engines.

In one aspect, the disclosure describes a device useful in determining abalancing solution for a high-pressure spool of a gas turbine engine.The device may comprise:

an input shaft configured to be coupled to an output of an accessorygear box driven by the high-pressure spool of the gas turbine engine;

a first trigger rotatably coupled to the input shaft at a first speedratio, the first speed ratio permitting a rotational speed of the firsttrigger to be substantially the same as a rotational speed of thehigh-pressure spool; and

a sensor configured to detect the trigger at each revolution of thetrigger and, upon detection of the trigger, generate one or more signalsrepresentative of each associated revolution of the high-pressure spoolof the gas turbine engine.

In another aspect, the disclosure describes a device useful indetermining a balancing solution for a high-pressure spool of a gasturbine engine. The device may comprise:

an interface configured to receive rotary input from an accessory gearbox driven by the high-pressure spool of the gas turbine engine; and

an output configured to generate one or more signals representative ofeach revolution of the high-pressure spool of the gas turbine engineassociated with the rotary input.

In a further aspect, the disclosure describes a method useful indetermining a balancing solution for a high-pressure spool of a gasturbine engine. The method may comprise:

generating one or more vibration signals representative of vibration ofthe high-pressure spool during operation of the gas turbine engine;

using an output of an accessory gear box of the gas turbine engineduring operation of the gas turbine engine, generating one or morerevolution signals representative of revolutions of the high-pressurespool associated with the output of the accessory gear box; and

using the one or more vibration signals and the one or more revolutionsignals, generating one or more signals useful in determining abalancing solution for the high-pressure spool.

Further details of these and other aspects of the subject matter of thisapplication will be apparent from the detailed description and drawingsincluded below.

DESCRIPTION OF THE DRAWINGS

Reference is now made to the accompanying drawings, in which:

FIG. 1 is a schematic, axial cross-section view of an exemplaryturbo-fan gas turbine engine;

FIG. 2 is a partial axial cross-section view of an exemplaryhigh-pressure spool of the gas turbine engine of FIG. 1;

FIG. 3 is an axonometric view of an exemplary phase device useful forbalancing the high-pressure spool of FIG. 2;

FIG. 4 is an axonometric view of exemplary gear trains of the phasedevice of FIG. 3;

FIG. 5 is a schematic representation of an exemplary sensor configuredto detect a rotatable trigger of the phase device of FIG. 3;

FIG. 6 is a schematic representation of an exemplary computing deviceconfigured to generate signals useful in determining a balancingsolution for the high-pressure spool of FIG. 2;

FIG. 7 is a flowchart illustrating an exemplary method useful inbalancing the high-pressure spool of FIG. 2;

FIGS. 8A and 8B respectively show exemplary vibration data andrevolution data plotted against a common time scale;

FIGS. 9A and 9B respectively show exemplary vibration data and phasedata plotted against the rotational speed of the high-pressure spool ofFIG. 2;

FIG. 10 is a schematic representation of an exemplary balancing rim ofthe high-pressure spool of FIG. 2 viewed along an axis of rotation ofthe high-pressure spool;

FIG. 11 is a schematic representation of the exemplary sensor andtrigger of FIG. 5 showing an angular offset between an angular positionof the trigger of the phase device and an angular position of areference point on the high-pressure spool of FIG. 2; and

FIG. 12 is another schematic representation of the balancing rim of FIG.10 viewed along the axis of rotation of the high-pressure spool withcorrection weights mounted thereon.

DETAILED DESCRIPTION

Aspects of various embodiments are described through reference to thedrawings.

FIG. 1 illustrates a gas turbine engine 10 of a type preferably providedfor use in subsonic flight, generally comprising in serial flowcommunication, fan 12 through which ambient air is propelled, multistagecompressor 14 for pressurizing the air, combustor 16 in which thecompressed air is mixed with fuel and ignited for generating an annularstream of hot combustion gases, and turbine section 18 for extractingenergy from the combustion gases.

Engine 10 may comprise a conventional or other type of gas turbineengine suitable for use in aircraft applications. For example, engine 10may comprise a turbofan or a turboprop type of engine. In variousembodiments, engine 10 may comprise a two-spool turbofan engine. Forexample, engine 10 may comprise high-pressure spool 20 and low-pressurespool 22. High-pressure spool 20 and low-pressure spool 22 may bemounted for rotation about axis CL of engine 10. High-pressure spool 20and low-pressure spool 22 may be mounted coaxially and rotate inopposite directions during use. High-pressure spool 20 may comprise oneor more high-pressure turbine stages 24 and one or more high-pressurecompressor stages 26. Low-pressure spool 22 may comprise one or morelow-pressure turbine stages 28 and fan 12.

Engine 10 may also comprise one or more accessory gear boxes 30(referred hereinafter as “AGB 30”) that may be used to drive one or moreaccessories (e.g., electrical generator, fuel pump, etc.) associatedwith the operation of engine 10 or with the operation of an aircraft(not shown) to which engine 10 may be mounted. AGB 30 may be driven byhigh-pressure spool 20 via tower shaft 32. FIG. 1 also shows phasedevice 34, which is described in detail below, and which may be coupledto and driven via AGB 30 during acquisition of data useful indetermining one or more balancing solutions for high-pressure spool 20while high-pressure spool 20 may be operated at typical operatingspeeds. Engine 10 may also comprise one or more vibration sensors 35.Vibration sensor(s) 35 may be disposed in different locations of engine10 to detect vibrations in different portions of engine 10. In variousembodiments, vibration sensor(s) 35 may be secured to one or morecasings of engine 10. For example, a plurality of vibration sensors 35may be disposed at spaced-apart locations along an axial direction ofengine 10. Vibration sensor(s) 35 may, for example, comprise anysuitable known or other type of transducer configured to generate one ormore signals representative of displacement, velocity and/oracceleration. In various embodiments, vibration sensor(s) 35 may be usedto obtain one or more velocity measurements as a function of time.

FIG. 2 is a partial axial cross-section view of high-pressure spool 20.In particular, FIG. 2 shows a portion of high-pressure spool 20associated with high-pressure turbine stages 24. As mentioned above,high-pressure turbine stages 24 may comprise first stage 24A and secondstage 24B. High-pressure spool 20 may comprise first (i.e., rear) coverplate 36 disposed on a downstream side of high-pressure turbine stage(s)24 and may include first balancing rim 38. High-pressure spool 20 mayalso comprise second cover plate 40 disposed on an upstream side ofhigh-pressure turbine stage(s) 24 and may include second balancing rim42. As explained further below, balancing rims 38 and 42 may beconfigured to permit the attachment of correction weights thereon tocounteract unbalances detected in high-pressure spool 20. High-pressurespool 20 may comprise one or more balancing rims or other balancingfeatures not shown in FIG. 2. For example, high-pressure spool 20 may,in some embodiments, comprise one or more additional balancing rimsspaced along an axial direction of high-pressure spool 20 in order topermit balancing of different axial portions of high-pressure spool 20,if necessary.

FIG. 3 is an axonometric view of an exemplary phase device 34 that maybe used during the acquisition of vibration data associated withhigh-pressure spool 20 under typical operating conditions of engine 10.Phase device 34 may comprise an interface for coupling to AGB 30. Forexample, such interface may comprise one or more input shafts 44(referred hereinafter as “input shaft 44”) and one or more mountingsurfaces 46 (referred hereinafter as “mounting surface 46”) forinterfacing with a mounting pad (not shown) of AGB 30. Accordingly,input shaft 44 may be configured to receive rotary input from an outputof AGB 30 driven by high-pressure spool 20 of engine 10. As explainedbelow, phase device 34 may be configured to generate one or more signalsrepresentative of each revolution of high-pressure spool 20 during theacquisition of vibration data based on the rotary input received fromAGB 30 via input shaft 44.

FIG. 4 is an axonometric view of exemplary gear trains 54, 56, 58 thatmay be part of phase device 34. Phase device 34 may be configured to beused on different types or families of engines 10. Accordingly, phasedevice 34 may comprise a plurality of outputs coupled to input shaft 44via different combinations of gears. For example, phase device 34 maycomprise a plurality of output shafts 48, 50 and 52 rotatably coupled toinput shaft 44. First output shaft 48 may be rotatably coupled to inputshaft 44 at a first speed (e.g., gear) ratio via first gear train 54comprising gears 54A, 54B, 54C and 54D. Second output shaft 50 may berotatably coupled to input shaft 44 at a second speed (e.g., gear) ratiovia second gear train 56 comprising gears 56A and 56B. Third outputshaft 52 may be rotatably coupled to input shaft 44 at a third speed(e.g., gear) ratio via third gear train 58 comprising gears 58A, 58B and58C. The presence of multiple output shafts 48, 50, 52 and associatedrespective gear trains 54, 56, 58 may permit phase device 34 to be usedon different types or families of gas turbine engines.

The first speed ratio obtained via gear train 54 between first outputshaft 48 and input shaft 44 may be configured to permit a rotationalspeed of first output shaft 48 to be substantially identical to arotational speed of high-pressure spool 20. In other words, gear train54 may be configured to, based on the rotational speed of input shaft44, reproduce the rotational speed of high-pressure spool 20 at outputshaft 48. Accordingly, gear train 54 may be configured for a specificconfiguration or type of AGB 30 and tower shaft 32. Second gear train 56and third gear train 58 may be configured for use in conjunction withother configurations or types of AGBs or tower shafts so that therotational speeds of high-pressure spools on other types or families ofengines may be reproduced via second output shaft 56 and third outputshaft 58. Accordingly, the presence of multiple output shafts 48, 50, 52may permit phase device 34 to be used in conjunctions with differentengines where the appropriate output shaft 48, 50, 52 would be used forthe specific engine with which phase device 34 may be used. Each outputshaft 48, 50, 52 may comprise a respective trigger 60, 62, 64. Triggers60, 62, 64 may be rotatable and detectable by one or more respectivesensors 66 (see FIG. 5). It should be understood that additional orfewer output shafts and associated gear trains may be provided in phasedevice 34 depending on the number or types or families of engines withwhich phase device 34 is to be used. For example, in some embodiments,phase device 34 may comprise a single output shaft 48 and associatedgear train 54.

FIG. 5 is a schematic representation of an exemplary sensor 66configured to detect one or more of triggers 60, 62, 64 on respectiveoutput shafts 48, 50, 52. An end view of an exemplary output shaft 48,50, 52 is shown in FIG. 5. In various embodiments, phase device 34 maycomprise a respective sensor 66 associated with each output shaft 48,50, 52 for detecting respective triggers 60, 62, 64. The types oftriggers 60, 62 and 64 and sensors 66 may be selected to cooperatetogether in generating one or more signals 68 when one of triggers 60,62 and 64 is detected by an associated sensor 66. Triggers 60, 62 and 64may comprise one or more markings, mechanical and/or magnetic featuresand/or other suitable type of feature(s) detectable by an associatedsensor 66. Similarly, sensor 66 may comprise one or more proximity,mechanical, optical and/or magnetic detectors and/or other suitable typeof sensor for detecting one or more of triggers 60, 62, 64.

In various embodiments, each output shaft 48, 50, 52 may comprise asingle respective trigger 60, 62, 64 that may be detectable by arespective sensor 66. For the purpose of the following description,output shaft 48 and trigger 60 will be referenced in conjunction withsensor 66 but it should be understood that, in some embodiments, thestructure and functions of output shafts 50, 52 and triggers 62, 64 withother respective sensors 66 may be substantially identical orfunctionally equivalent. Trigger 60 may be secured to, integral with orotherwise associated with output shaft 48 so that trigger 60 may rotatetogether and at the same rotational speed as output shaft 48.Accordingly, trigger 60 may pass and be detected by sensor 66 once forevery complete revolution of output shaft 48. Upon detection of thepassing of rotating trigger 60, sensor 66 may output one or morerevolution signals 68. Since the rotational speed of output shaft 48 maybe substantially identical to the rotational speed of high-pressurespool 20 (i.e., sometimes referred as “N2”), each complete revolution oftrigger 60 may correspond to an associated complete revolution ofhigh-pressure spool 20. Accordingly, revolution signal(s) 68 generatedby sensor 66 upon detection of trigger 60 may consequently berepresentative of an associated revolution of high-pressure spool 20. Invarious embodiments, revolution signal(s) 68 may comprise one or moreonce-per-revolution signals where consecutive once-per-revolutionsignals may indicate the completion of consecutive revolutions ofhigh-pressure spool 20.

FIG. 6 is a schematic representation of an exemplary computing device 70configured to generate one or more signals 72 representative of at leastpart of a balancing solution for high-pressure spool 20. In variousembodiments, computing device 70 may comprise one or more dataprocessors 74 (referred hereinafter as “processor 74”) and one or morememories 76 (referred hereinafter as “memory 76”). For example,computing device 70 may comprise one or more digital computer(s) orother data processors and related accessories. Data processor 74 mayinclude one or more microcontrollers, microprocessors or other suitablyprogrammed or programmable logic circuits. Memory 76 may comprise anystorage means (e.g. devices) suitable for retrievably storingmachine-readable instructions executable by processor 74. Memory 76 maycomprise, for example, but is not limited to, an electronic, magnetic,optical, electromagnetic, infrared, or semiconductor system, apparatusor device. More specific examples, but nonetheless a non-exhaustivelist, of memory 76 would include the following: a portable computerdiskette (magnetic), a RAM (electronic), a read-only memory “ROM”(electronic), an erasable programmable read-only memory (EPROM or Flashmemory) (electronic) and a portable compact disc read-only memory“CDROM” (optical).

Memory 76 may contain machine-readable instructions for execution byprocessor 74. Such machine-readable instructions may cause processor 74to carry out various methods or portion of methods disclosed herein. Invarious embodiments, signals 78 representative of vibration ofhigh-pressure spool 20 may be generated by one or more vibration sensors35 (referred hereinafter as “vibration sensor 35”) and provided directlyor indirectly to computing device 70. Similarly, revolution signal(s) 68may be generated by sensor 66 and provided directly or indirectly tocomputing device 70. It should be understood that, in some embodiments,suitable conditioning of signals 78, 68 may be required prior toprocessing by processor 74. Using vibration signals 78 and revolutionsignals 68, data processor 74 may, in accordance with computer-readableinstructions stored in memory 76, generate one or more signals 72representative of at least part of the balancing solution. For example,signals 72 may be representative of: vibration data including one ormore vibration peaks. Such vibration data may include time valuesassociated with discrete vibration measurements (i.e., magnitudes) andthe time values may be associated with a common time scale as timevalues associated with revolution signals 68. Accordingly, suchvibration data may be correlated to revolution signals 68 via a commontime scale. In various embodiments, signals 72 may be useful indetermining one or more correction weights and one or more correspondingtimes to or from once-per-revolution signal(s) from revolution signals68. Alternatively or in addition, signals 72 may be representative ofone or more correction weights and one or more corresponding angularpositions of trigger 60 relative to sensor 66 and/or one or morecorresponding angular positions on a balancing rim 38, 42 ofhigh-pressure spool 20. For example, computing device 70 may, inaccordance with computer-readable instructions provided in memory 76,consider one or more correlations 80 between the angular position oftrigger 60 and the angular position of high-pressure spool 20 so thatsignal(s) 72 may be indicative of one or more correction weightssuitable to remedy one or more unbalance conditions of high-pressurespool 20 together with one or more angular positions on balancing rim38, 42 of high-pressure spool 20. In various embodiments, such signal(s)72 may provide some indication useful for the installation of one ormore correction weights on high-pressure spool 20.

In order to determine a balancing solution for a rotor, vibrationmagnitude and phase data are typically required. In most two-spool gasturbine engines, the phase data of the high-pressure spool is notavailable during normal operation. Accordingly, the acquisition ofvibration and phase data for the balancing of the high-pressure spool istypically conducted while the high-pressure spool is rotated at sub-idlespeeds and also while the engine is partially disassembled in order toexpose a portion of the high-pressure spool. Since the dynamiccharacteristics of the high-pressure spool can be quite different atfull operating speeds than they are at reduced, sub-idle speeds, thebalancing solution acquired under such reduced speed conditions may notnecessarily be ideal for typical operating conditions of such gasturbine engines.

During operation, phase device 34 and, optionally, computing device 70may be used in the determination of a balancing solution forhigh-pressure spool 20. In various embodiments, the acquisition ofvibration signal(s) 78 may be conducted using vibration sensor 35 undertypical operating conditions of engine 10 and at typical operatingrotational speeds of high-pressure spool 20 while phase device 34 iscoupled to AGB 30. Phase device 34 may be installed to an accessory padof AGB 30 via mounting surface 46 and input shaft 44 may be coupled toan output of AGB 30. Phase device 34 may be mounted to a free accessorypad of AGB 30 or an existing accessory may be removed so that phasedevice 34 may be installed in its place. For example, the acquisition ofvibration signal(s) 78 may be conducted at typical operating rotationalspeeds of high-pressure spool 20 so that the balancing solution(s)determined may take into account the dynamic characteristics ofhigh-pressure spool 20 at typical operating speeds. Similarly, theacquisition of vibration signal(s) 78 may be conducted over a range ofrotational speeds of high-pressure spool 20 so that the balancingsolution(s) determined may take into account the dynamic characteristicsof high-pressure spool 20 in different operating regimes. In variousembodiments, the acquisition of vibration signal(s) 78 may, for example,be conducted while engine 10 is in a test cell or when engine 10 ison-wing (e.g., in the field). For example, the acquisition of vibrationsignal(s) 78 and or revolution signal(s) 68 may be acquired duringoperation of engine 10 and the balancing solution(s) may be determinedsubsequently.

In various embodiments, vibration signal(s) 78 acquired via vibrationsensor 35 may comprise components that represent vibrations from sourcesother than high-pressure spool 20. For example, vibration signal(s) 78may represent substantially all of the vibrations that may be sensed byvibration sensor 35 whether or not they originate from high-pressurespool 20. Accordingly, some filtering or other processing of vibrationsignal(s) 78 may be required to isolate the component(s) that is/arerepresentative of vibrations associated with high-pressure spool 20.Filtering or other processing of vibration signal(s) 78 may be conductedaccording to known or other methods. For example, vibration signal(s) 78may be filtered through the use of engine order analysis of the specificspeed(s) of interest (e.g., the rotational speed N2 of high-pressurespool 20). Accordingly, the frequency and phase information ofvibrations stemming from other sources may be filtered out fromvibration signal(s) 78 or otherwise ignored in the determination of abalancing solution for high-pressure spool 20.

FIG. 7 is a flowchart illustrating an exemplary method 700 which may beuseful determining one or more balancing solutions for high-pressurespool 20. In various embodiments, method 700 may comprise: generatingone or more vibration signals 78 representative of vibration ofhigh-pressure spool 20 during operation of gas turbine engine 10 (seeblock 702); using an output of AGB 30 of gas turbine engine 10 duringoperation of gas turbine engine 10, generating one or more revolutionsignals 68 representative of revolutions of high-pressure spool 20associated with the output of AGB 30 (see block 704); and using the oneor more vibration signals 78 and the one or more revolution signals 68,generating one or more signals 72 useful in determining a balancingsolution for high-pressure spool 72. In various embodiments, method 700or portions thereof may be performed using phase device 34, vibrationsensor(s) 35 and/or computing device(s) 70. It should be understood thatmethod 700 may comprise additional or fewer steps or blocks than thoseshown in FIG. 7. There may be many variations to these blocks and/oroperations without departing from the teachings of the presentdisclosure. For instance, the blocks may be performed in a differingorder, or blocks may be added, deleted, or modified. As explained abovesignal(s) 72 may useful in determining one or more balancing solutionsfor high-pressure spool 20 and may be representative of a partialbalancing solution helpful in selecting one or more correction weightsand its/their associated position(s) on the high-pressure spool 20.

In various embodiments, the generating of revolution signal(s) 68 maycomprise converting a rotational speed of the output of AGB 30 to arotational speed substantially identical to the rotational speed ofhigh-pressure spool 20. As explained above, this may be conducted viaoutput shaft 48 and associated gear train 54 of phase device 34. Thegenerating of revolution signal(s) 68 may comprise detecting trigger 60associated with output shaft 48 and having substantially the samerotational speed as that of high-pressure spool 20. Revolution signal(s)68 may be based on the detection of a single trigger 60 havingsubstantially the same rotational speed as that of high-pressure spool20. Accordingly, revolution signal(s) 68 may comprise one or moreonce-per-revolution signals where two consecutive once-per-revolutionsignals may indicate a complete revolution of high-pressure spool 20.

As explained above, phase device 34 may comprise a plurality ofrotatable triggers 60, 62, 64 so that phase device 34 may be used inconjunction with other types or families of engines. Accordingly, method700 may further comprise: driving first rotatable trigger 60 using theoutput of AGB 30 at a first speed ratio with the output of AGB 30;driving second rotatable trigger 62 using the output of AGB 30 at asecond speed ratio with the output of AGB 30; and generating revolutionsignal(s) 68 based on the detection (e.g., via sensor(s) 66) of one offirst rotatable trigger 60 and second rotatable trigger 62. In someembodiments, the first speed ratio may be configured to permit arotational speed of first trigger 60 to be substantially identical as arotational speed of high-pressure spool 20 and the second speed ratiomay be configured to permit a rotational speed of second trigger 62 tobe substantially the same as a rotational speed of a high-pressure spoolof another gas turbine engine when phase device 34 is used with theother gas turbine engine.

FIGS. 8A and 8B respectively show exemplary plots of vibration signal(s)78 and revolution signal(s) 68 plotted against a common time scale.Vibration signal(s) 78 may comprise one or more vibration magnitudessensed using vibration sensor(s) 35. Some or all of the vibrationmagnitudes may be associated with corresponding time valuessubstantially representing the time at which individual vibrationmagnitudes were sensed. In various embodiments, vibration signal(s) 78may be representative of velocities (e.g., in/sec, m/s) plotted againsttime. Vibration signal(s) 78 may stem from one vibration sensor 35 ormay comprise a combination or aggregation of vibration signals obtainedfrom different vibration sensors 35. Revolution signal(s) 68 maycomprise one or more pulses 82 indicating the detection of trigger 60 bysensor 66. Revolution signal(s) 68 may be generated simultaneously withthe generation of vibration signal(s) 78. Consecutive pulses 82 inrevolution signal(s) 68 as shown in FIG. 8B may be indicative ofcomplete revolutions of trigger 60 and consequently be indicative ofcomplete revolutions of high-pressure spool 20. Accordingly, pulses 82may be once-per-revolution signals. Pulses 82 may each be associatedwith a time value substantially representing the time at which trigger60 was sensed by sensor 66. Accordingly, vibration signal(s) 78 may becorrelated with revolution signal(s) 68 based on the common time scale(i.e., abscissa in FIGS. 8A and 8B). Also since the time durationbetween two consecutive pulses 82 may represent a complete revolution(i.e., 360 degrees) of trigger 60, vibration magnitudes of signal(s) 78may be correlated (e.g., synchronized) to angular position(s) of trigger60 relative to the position of sensor 66.

FIGS. 9A and 9B respectively show exemplary vibration data and phasedata plotted against the rotational speed of high-pressure spool 20. Asexplained above, the acquisition of vibration signal(s) 78 may beconducted at different rotational speeds of high-pressure spool 20 inorder to take into account the dynamic properties of high-pressure spool20 at different rotational speeds. Accordingly, a vibration sweep may beconducted to acquire vibration signal(s) 78 over a range of rotationalspeeds of high-pressure spool 20. FIG. 9A shows a plot of the phase oftrigger 60 (in degrees), at which peak vibration magnitudes (obtainedfrom vibration signal(s) 78) occur over a range of rotational speeds(i.e., N2) of high-pressure spool 20. FIG. 9B shows a plot of associatedpeak vibration magnitudes (in in/sec) plotted against the same range ofrotational speeds (i.e., N2) of high-pressure spool 20. FIG. 9Bindicates that, for this particular example, the largest vibrationmagnitude over the particular range of rotational speeds is 0.42 in/secand occurs at about 22,000 rpm. FIG. 9A indicates that the correspondingphase of trigger 60 at which the largest vibration magnitude occurs isabout 320°. This information may be used as a basis for determining asuitable correction weight to be installed on high-pressure spool 20.

During installation of phase device 34 to AGB 30, it may not benecessary to establish the angular relationship between the output ofAGB 30 and high-pressure spool 20 at least initially. This relativeangular position may be assessed, following all data collection andafter some disassembly of engine 10 (e.g., via the first cover plate 36of high-pressure shaft 20). Once phase device 34 has been synchronizedto high-pressure spool 20, the vibration data (i.e. magnitude and phase)from actual operating speeds can be used to balance high-pressure spool20. Accordingly, phase device 34 may be used when acquiring vibrationdata when engine 10 is in a test cell, during an engine overhaul and/orin the field with engine 10 mounted on-wing.

FIG. 10 is a schematic view of first balancing rim 38 of first coverplate 36 viewed along axis CL of FIG. 2. First balancing rim 38 maycomprise a plurality of holes (e.g., numbered as numbers 1-40 in FIG.10) which may be used to secure one or more correction weights to firstbalancing rim 38. The holes may be spaced about the circumference offirst balancing rim 38. The angular position of each hole is alsoindicated in degrees in FIG. 10. First cover plate 36 may also compriseone or more reference markers sometimes called Phi marks (referredhereinafter as “Phi mark 84”). Phi mark 84 may be used to angularlyalign high-pressure spool 20 to a reference position (e.g., anotherreference mark). In various embodiments, the reference angular positionof high-pressure spool 20 in engine 10 may be a location where Phi mark84 is substantially aligned with a top dead center (TDC) of engine 10.The angular positions of holes in FIG. 10 may be measured from Phi mark84.

In order to correlate the phase data (shown in FIG. 9A and based onangular position of trigger 60) to one or more corresponding holes infirst balancing rim 38, an angular offset between trigger 60 and firstbalancing rim 38 may be determined. Vibration signal(s) 78 may beacquired relative to trigger 60 and subsequently correlated tohigh-pressure spool 20 after the acquisition of vibration signal(s) 78has been completed. Accordingly, the determination of one or morebalancing solutions may also be carried out subsequently. In variousembodiments, the determination of the offset between trigger 60 of phasedevice 34 and first balancing rim 38 may be performed by maintenancepersonnel when engine 10 is not operating. Some disassembly of engine 10may be required in order to at least partially expose first balancingrim 38 to maintenance personnel.

FIG. 11 is a schematic representation of sensor 66 and trigger 60showing an exemplary angular offset of 120° between an angular positionof trigger 60 of phase device 34 relative to sensor 66 and TDC ofhigh-pressure spool 20. For example, high-pressure shaft 20 may be(e.g., manually) rotated until Phi mark 84 is substantially aligned withTDC. While, high-pressure spool 20 is at this position, the angularoffset between trigger 60 and sensor 66 may be determined. The angularoffset may be determined by slowly rotating (e.g., clockwise) firstbalancing rim 38 from TDC until trigger 60 of phase device 34 is sensedby sensor 66. When sensor 66 detects trigger 60, an audio and/or visualindication or alert may provide a signal to maintenance personnelindicating the position at which to determine the offset. Once trigger60 is sensed by sensor 66, the corresponding angular position ofbalancing rim 38 relative to TDC may be determined via markings and/orholes provided on first cover plate 36 or via other suitable means. Theangular offset may then be used to transfer the phase data of trigger 60to high-pressure spool 20 in order to determine the angular position(s)on first balancing rim 38 at which one or more correction weights may beinstalled. In other words, the determination of the balancing solutionfor high-pressure spool 20 may be based on a first correlation betweenvibration signal(s) 78 and revolution signal(s) 68 and on a secondcorrelation between revolution signal(s) 68 and angular positioning onhigh-pressure spool 20.

Once the angular/phase offset between phase device 34 and high-pressurespool 20 has been determined, one or more suitable balancing solutionsmay be determined based on vibration signal(s) 68. Suitable balancingsolutions may be determined using known or other methods. In variousembodiments, a balancing solution (e.g., correction weight andassociated angular position) may be determined according to therelationship shown below. An numerical example is also provided belowusing the exemplary numerical values disclosed herein.

$\begin{matrix}{{{Correction}\mspace{14mu} {Weight}} = \frac{{- {Baseline}}\mspace{14mu} {Vibration}\mspace{14mu} {Vector}}{{Balancing}\mspace{14mu} {Influence}\mspace{14mu} {Coefficient}}} \\{= \frac{0.42\mspace{14mu} {in}\text{/}s\; {\angle\left( {320 - 180 + \overset{\overset{{Phase}\mspace{14mu} {box}\mspace{14mu} {offset}}{\downarrow}}{120{^\circ}}} \right)}}{0.14\mspace{14mu} {in}\text{/}{s/{gram}}\; \angle \; 270{^\circ}}} \\{= {3.0\mspace{14mu} {grams}\; \angle \; 110{^\circ}}}\end{matrix}$

FIG. 12 is another schematic representation of first balancing rim 38with three correction weights labeled as “H”. The correction weightshave been installed on first balancing rim 38 via holes #26, #28 and #31at 130°, 112° and 85° respectively.

The above description is meant to be exemplary only, and one skilled inthe relevant arts will recognize that changes may be made to theembodiments described without departing from the scope of the inventiondisclosed. For example, the blocks and/or operations in the flowchartsand drawings described herein are for purposes of example only. Theremay be many variations to these blocks and/or operations withoutdeparting from the teachings of the present disclosure. For instance,the blocks may be performed in a differing order, or blocks may beadded, deleted, or modified. The present disclosure may be embodied inother specific forms without departing from the subject matter of theclaims. Also, one skilled in the relevant arts will appreciate thatwhile the systems, devices and assemblies disclosed and shown herein maycomprise a specific number of elements/components, the systems, devicesand assemblies could be modified to include additional or fewer of suchelements/components. The present disclosure is also intended to coverand embrace all suitable changes in technology. Modifications which fallwithin the scope of the present invention will be apparent to thoseskilled in the art, in light of a review of this disclosure, and suchmodifications are intended to fall within the appended claims.

1. A device useful in determining a balancing solution for ahigh-pressure spool of a gas turbine engine, the device comprising: aninput shaft configured to be coupled to an output of an accessory gearbox driven by the high-pressure spool of the gas turbine engine; a firsttrigger rotatably coupled to the input shaft at a first speed ratio, thefirst speed ratio permitting a rotational speed of the first trigger tobe substantially the same as a rotational speed of the high-pressurespool; and a sensor configured to detect the trigger at each revolutionof the trigger and, upon detection of the trigger, generate one or moresignals representative of each associated revolution of thehigh-pressure spool of the gas turbine engine.
 2. The device as definedin claim 1, comprising a second trigger rotatably coupled to the inputshaft at a second speed ratio, the second speed ratio permitting arotational speed of the second trigger to be substantially identical toa rotational speed of a high-pressure spool of another gas turbineengine when the device is used with the other gas turbine engine.
 3. Adevice useful in determining a balancing solution for a high-pressurespool of a gas turbine engine, the device comprising: an interfaceconfigured to receive rotary input from an accessory gear box driven bythe high-pressure spool of the gas turbine engine; and an outputconfigured to generate one or more signals representative of eachrevolution of the high-pressure spool of the gas turbine engineassociated with the rotary input.
 4. The device as defined in claim 3,wherein: the interface comprises an input shaft; and the devicecomprises a first detectable trigger coupled to the input shaft at afirst speed ratio.
 5. The device as defined in claim 4, wherein thefirst speed ratio is configured to permit a rotational speed of thefirst trigger to be substantially identical to a rotational speed of thehigh-pressure spool.
 6. The device as defined in claim 5, comprising asensor configured to detect the trigger at each revolution of thetrigger and, upon detection of the trigger, generate one or more signalsrepresentative of each associated revolution of the high-pressure spoolof the gas turbine engine.
 7. The device as defined in claim 5,comprising a second detectable trigger coupled to the input shaft at asecond speed ratio, the second speed ratio permitting a rotational speedof the second trigger to be substantially identical to a rotationalspeed of a high-pressure spool of another gas turbine engine when thedevice is used with the other gas turbine engine.
 8. The device asdefined in claim 3, comprising a first trigger coupled to the interfaceand configured to cause the generation of the one or more signals by theoutput.
 9. The device as defined in claim 3, comprising a rotatabletrigger coupled to the interface and configured to substantiallyreproduce a rotational speed of the high-pressure spool based on therotary input from the accessory gear box.
 10. The device as defined inclaim 9, comprising a sensor configured detect the trigger at eachrevolution of the trigger and, upon detection of the trigger, generateone or more signals representative of each associated revolution of thehigh-pressure spool of the gas turbine engine. 11.-20. (canceled)